Sigma APO 500mm F4.5 EX DG HSM Lens

By adding an APO teleconverter (optional extra), you can use this lens as a 700mm f6.3 MF ultra-telephoto lens with a 1.4X EX teleconverter, or as a 1000mm F9 MF ultra-telephoto lens with a 2X teleconverter. 
This ultra-telephoto lens has a fast maximum aperture, and also features a new super multi-layer coating, which optimizes the characteristics of digital SLR cameras. Two ELD glass elements in the front lens elements reduce chromatic aberration to a minimum and also ensure sharp, quality images of high contrast. 
The improved DG lens design corrects for various aberrations. This lens is specially coated to get the best color balance whilst cutting down on ghosting caused by reflections from the digital image sensor. The lens provides the utmost correction against lateral chromatic aberration which is a serious problem for digital SLR cameras.

Key Features
- Powerful and silent Hyper Sonic Motor enables fulltime manual focus override. 
- EX lens series denotes excellence of engineering and new technology. 
- A rotatable 46mm drop-in filter holder in the rear part of the lens barrel facilitates the use of filters including a polarizing filter.